man3/usleep.3

   1 .\" Copyright 1993 David Metcalfe (david@prism.demon.co.uk)
   2 .\"
   3 .\" SPDX-License-Identifier: Linux-man-pages-copyleft
   4 .\"
   5 .\" References consulted:
   6 .\"     Linux libc source code
   7 .\"     Lewine's _POSIX Programmer's Guide_ (O'Reilly & Associates, 1991)
   8 .\"     386BSD man pages
   9 .\" Modified 1993-07-24 by Rik Faith (faith@cs.unc.edu)
  10 .\" Modified 2001-04-01 by aeb
  11 .\" Modified 2003-07-23 by aeb
  12 .\"
  13 .TH usleep 3 (date) "Linux man-pages (unreleased)"
  14 .SH NAME
  15 usleep \- suspend execution for microsecond intervals
  16 .SH LIBRARY
  17 Standard C library
  18 .RI ( libc ", " \-lc )
  19 .SH SYNOPSIS
  20 .nf
  21 .B "#include <unistd.h>"
  22 .PP
  23 .BI "int usleep(useconds_t " usec );
  24 .fi
  25 .PP
  26 .RS -4
  27 Feature Test Macro Requirements for glibc (see
  28 .BR feature_test_macros (7)):
  29 .RE
  30 .PP
  31 .BR usleep ():
  32 .nf
  33     Since glibc 2.12:
  34         (_XOPEN_SOURCE >= 500) && ! (_POSIX_C_SOURCE >= 200809L)
  35             || /* Glibc since 2.19: */ _DEFAULT_SOURCE
  36             || /* Glibc <= 2.19: */ _BSD_SOURCE
  37     Before glibc 2.12:
  38         _BSD_SOURCE || _XOPEN_SOURCE >= 500
  39 .\"    || _XOPEN_SOURCE && _XOPEN_SOURCE_EXTENDED
  40 .fi
  41 .SH DESCRIPTION
  42 The
  43 .BR usleep ()
  44 function suspends execution of the calling thread for
  45 (at least) \fIusec\fP microseconds.
  46 The sleep may be lengthened slightly
  47 by any system activity or by the time spent processing the call or by the
  48 granularity of system timers.
  49 .SH RETURN VALUE
  50 The
  51 .BR usleep ()
  52 function returns 0 on success.
  53 On error, \-1 is returned, with
  54 .I errno
  55 set to indicate the error.
  56 .SH ERRORS
  57 .TP
  58 .B EINTR
  59 Interrupted by a signal; see
  60 .BR signal (7).
  61 .TP
  62 .B EINVAL
  63 \fIusec\fP is greater than or equal to 1000000.
  64 (On systems where that is considered an error.)
  65 .SH ATTRIBUTES
  66 For an explanation of the terms used in this section, see
  67 .BR attributes (7).
  68 .ad l
  69 .nh
  70 .TS
  71 allbox;
  72 lbx lb lb
  73 l l l.
  74 Interface       Attribute       Value
  75 T{
  76 .BR usleep ()
  77 T}      Thread safety   MT-Safe
  78 .TE
  79 .hy
  80 .ad
  81 .sp 1
  82 .SH STANDARDS
  83 4.3BSD, POSIX.1-2001.
  84 POSIX.1-2001 declares this function obsolete; use
  85 .BR nanosleep (2)
  86 instead.
  87 POSIX.1-2008 removes the specification of
  88 .BR usleep ().
  89 .PP
  90 On the original BSD implementation,
  91 and in glibc before version 2.2.2, the return type of this function is
  92 .IR void .
  93 The POSIX version returns
  94 .IR int ,
  95 and this is also the prototype used since glibc 2.2.2.
  96 .PP
  97 Only the
  98 .B EINVAL
  99 error return is documented by SUSv2 and POSIX.1-2001.
 100 .SH NOTES
 101 The interaction of this function with the
 102 .B SIGALRM
 103 signal, and with other timer functions such as
 104 .BR alarm (2),
 105 .BR sleep (3),
 106 .BR nanosleep (2),
 107 .BR setitimer (2),
 108 .BR timer_create (2),
 109 .BR timer_delete (2),
 110 .BR timer_getoverrun (2),
 111 .BR timer_gettime (2),
 112 .BR timer_settime (2),
 113 .BR ualarm (3)
 114 is unspecified.
 115 .SH SEE ALSO
 116 .BR alarm (2),
 117 .BR getitimer (2),
 118 .BR nanosleep (2),
 119 .BR select (2),
 120 .BR setitimer (2),
 121 .BR sleep (3),
 122 .BR ualarm (3),
 123 .BR useconds_t (3type),
 124 .BR time (7)